diff --git a/scripts/auto-close-duplicates.ts b/scripts/auto-close-duplicates.ts
index 2ad3bd3112..32e77db97c 100644
--- a/scripts/auto-close-duplicates.ts
+++ b/scripts/auto-close-duplicates.ts
@@ -77,10 +77,18 @@ async function closeIssueAsDuplicate(
     {
       state: 'closed',
       state_reason: 'duplicate',
-      labels: ['duplicate']
     }
   );
 
+  // Add the duplicate label additively — PATCH with `labels` replaces the
+  // entire label set, which would erase platform/area/priority metadata.
+  await githubRequest(
+    `/repos/${owner}/${repo}/issues/${issueNumber}/labels`,
+    token,
+    'POST',
+    { labels: ['duplicate'] }
+  );
+
   await githubRequest(
     `/repos/${owner}/${repo}/issues/${issueNumber}/comments`,
     token,